RC structures cyclic behavior simulation with a model integrating plasticity, damage, and bond-slip

The behavior of reinforced concrete structures under severe demands, as strong ground motions, is highly complex; this is mainly due to the complexity of concrete behavior and to the strong interaction between concrete and steel, with several coupled failure modes. On the other hand, given the increasing awareness and concern on the worldwide seismic risk, new developments have arisen in earthquake engineering; nonetheless, some developments are mainly based on simple analytical tools that are widely used, given their moderate computational cost. This research aims to provide a solid basis for validation and calibration of such developments by using computationally efficient continuum mechanics-based tools. Within this context, this paper presents a model for 3D simulation of cyclic behavior of RC structures. The model integrates a bond-slip model developed by one of the authors and the damage variable evolution methodology for concrete damage plastic model developed by some authors. In the integrated model, a new technique is derived for efficient 3D analysis of bond-slip of 2 or more crossing reinforcing bars in beam-column joints, slabs, footings, pile caps, and other similar members. The analysis is performed by implementing the bond-slip model in a user element subroutine of Abaqus and the damage variable evolution methodology in the original concrete damage plastic model in the package. Two laboratory experiments consisting of a column and a frame subjected to cyclic displacements up to failure are simulated with the proposed formulation

Numerical modeling of the tension stiffening in reinforced concrete members via discontinuum models

[prova tipográfica]This study presents a numerical investigation on the fracture mechanism of tension stiffening phenomenon in reinforced concrete members. A novel approach using the discrete element method (DEM) is proposed, where three-dimensional randomly generated distinct polyhedral blocks are used, representing concrete and one-dimensional truss elements are utilized, representing steel reinforcements. Thus, an explicit representation of reinforced concrete members is achieved, and the mechanical behavior of the system is solved by integrating the equations of motion for each block using the central difference algorithm. The inter-block interactions are taken into consideration at each contact point with springs and cohesive frictional elements. Once the applied modeling strategy is validated, based on previously published experimental findings, a sensitivity analysis is performed for bond stiffness, cohesion strength, and the number of truss elements. Hence, valuable inferences are made regarding discontinuum analysis of reinforced concrete members, including concrete-steel interaction and their macro behavior. The results demonstrate that the proposed phenomenological modeling strategy successfully captures the concrete-steel interaction and provides an accurate estimation of the macro behavior

Alternate reinforcements for enhanced corrosion resistance in TxDOT bridges: final report

The corrosion of reinforcing steel in concrete is the leading cause of deterioration for reinforced concrete structures, especially bridges exposed to external chlorides. Practitioners and researchers have evaluated and implemented various technologies to combat this problem, including the use of high-performance concrete, chemical corrosion inhibitors, sealers and barriers, and alternative reinforcement. This synthesis project addressed the latter, specifically the use of alternative reinforcement (e.g., fiber-reinforced polymer (FRP) reinforcement, epoxy-coated steel, stainless steel, galvanized steel, etc.) to extend the service life of bridge structures subjected to external chlorides from marine environments or from de-icing salt applications. The primary goals of this project were to (a) review and synthesize published literature, (b) review and synthesize current DOT practice, (c) identify gaps in our current knowledge and state of practice, and (d) provide guidance, based on current knowledge, on how to evaluate and select alternative reinforcement for bridges subjected to external chlorides.Preprin